This invention relates generally to antenna systems and specifically to antenna systems for receiving digital ATV (Advanced television) signals, as recently adopted by the FCC for broadcast communications, that are in and above the UHF frequency range.
The recently approved digital ATV signals have a vestigial sideband (VSB) form and are designed to operate in the vicinity of NTSC cochannel signals with minimal interference. The digital signals will initially be of relatively low power, especially within an indoor environment and, consequently, there is a need for efficient indoor antenna systems, replacing the ubiquitous dipoles and "bowties". In particular, the response of the antenna system should be uniform across the frequency band and adaptable to minimize the effects of multipath signal propagation. Multipath refers to the condition where a transmitted signal is reflected by buildings, objects and the like to create one or more signals that are not coherent with the main signal. Because the VSB signal does not have the redundancy of an NTSC signal, receiving and demodulating systems are more critical due to the "cliff effect". It is therefore of great importance that signal reception be efficient, especially for transmitted signals in the UHF frequency range, where problems of reflection and multipath become paramount.
The present invention provides an adaptive antenna system that is adjustable to optimize signal reception by utilizing the best combination of antenna polarization and directivity. While the described embodiment of the invention is directed to a television environment, it will be appreciated by those skilled in the art that the invention is applicable to any signal receiving system that exhibits similar needs.